Experienced gunsmiths and shooters know the value of an adjustable gas block on gas operated AR-15 rifles and carbines. If the AR is overgassed it delivers excessive recoil to the shooter, and will slam cycle the firearm until it breaks. If it is undergassed, it will not function reliably. Both situations are bad.

There is no cure all due to the fact that there are a wide variety of guns, ammo, and shooting styles. Every firearm and ammunition combination performs best when it is individually tuned for optimum cycling reliability. This means the firearm needs enough gas to operate reliably, but not so much gas that it slam cycles.

In the past, porting the barrel was a matter of trial and error. If you went to far, there was no throttling back option available, and the barrel often had to be replaced. Changing ammo was another problem. One gas port size might work fine with one particular load, then be over or under gassed with another load. Changing the port size normally meant deep disassembly of a rifle which may already have the final finish applied. This commonly left finish scars on the rifle, gas leaks, and did nothing to help when a different kind of ammo was used in the future.

A couple of different methods of external gas adjustments have been tried over the years, but they failed to be field reliable, as they would not hold their settings, and thus led to unreliability. Loctiting a gas setting is not a durable option because the gas block quickly heats when firing and melts the loctite. A better design was required.

The D&L gas block design solves the problems which have become evident over years of experience with the AR system. The DLAGB is cross clamped across the bottom of the barrel with three large cross bolts to seal off any gas leaks. The DLAGB features pilot holes which allow countersinking lock screws into the barrel to assure the gas block will not rotate out of alignment with the gas port and cause reliability and POA / POI problems. The top of the gas block is machined into a picatinny rail so a front sight or other accessory can be used. The gas flow through the system can be regulated during the construction and test firing of the rifle, and adjusted by the knowledgeable operator in the future. Importantly, once the gas is properly regulated, the setting can be mechanically locked in place.

The proper point in gas regulation can often be determined by observing the brass being ejected from the rifle. Brass ejecting into the 3 o'clock to 5 o'clock region generally indicates a well regulated rifle.

The DLAGB is available for two barrel sizes ; .750" and .936" O.D. in the area of the gas port. The blocks are matte black aluminum.